As the third generation of rare earth permanent magnet materials, neodymium-iron-boron (Nd—Fe—B) features high residual magnetism Br, high coercive force Hcj and high magnetic energy product (BH)m. So, it makes market immediately once such features are discovered, and becomes one of the key materials for modern science and technology development, and metal Nd in Nd—Fe—B magnet takes 90% or above of the cost of the raw materials. With the constant increase of the yield of rare earth permanent magnet all over the world, the utilization amount of metal Nd increases greatly, imposing great pressure on magnetic material manufacturers and users. Therefore, there is an urgent need to develop a novel permanent magnet alloy. Beside Nd, metal Ce among the natural rare earth resources features rich reserve and low cost. But, the magnetic torque Js and anisotropic field HA of Ce2Fe14B falls far below those of Nd2Fe14B, and the basic magnetic parameters of a Ce2Fe14B phase are calculated in the article [IEEE Trans. On Magn; 1984 MAG-20(5): 1584]. It is impossible to meet the requirements of user's on performance when Ce2Fe14B magnet is prepared by using a traditional preparation method. At present, most of the patents regarding Ce-containing magnet is featured by the fact that Nd in Nd2Fe14B is partly substituted by Ce and the content of Ce is typically not more than 40%, for example: in the patent CN1035737A of Central Steel & Iron Research Institute under Ministry of Metallurgical Industry, the content of Ce is not more than 30%; although Ce is added in the documents [J. Magn. Magn. Mater. 294, e127 (2005)] and [J. Appl. Phys. 105, 07A704 (2009)], the content of Ce is not more than 20%; the content of Ce is up to 40% in the patents CN102220538A and CN101694797 of Magnequench (Tianjin) Co., Ltd., furthermore, its preparation process used is different from that in the present invention, and the final product is isotropic magnetic powder instead of anisotropic magnet; the content of Ce rises to 40% in the article [J. Appl. Phys. 75, 6268 (1994)], but what this article focuses on is silicon (Si)-containing magnet, and a single alloy process is used, which is different from the present invention in aspects of composition and process. The majority of above patents and periodical documents lie in the adoption of a preparation method for directly smelting Ce into alloy, so that Nd in a main phase is substituted by Ce excessively to deteriorate the performance of magnet severely, and the residual magnetism, coercive force and magnetic energy product of a final product are all low.
In the prior art, preparation processes of a Ce permanent magnet alloy typically adopt a single alloy method and a double alloy method (also referred to as ‘a liquid phase-added sintering method’). In these methods, the single alloy method is as follows: a fixed amount of metal Ce is added at the stage of alloy material mixing, Ce, Nd, Fe, B and other doping elements are mixed and smelted to obtain an alloy ingot with a single component, and then a traditional powder metallurgical sintering process is employed for preparing magnet. The double alloy method is as follows: a main phase alloy and an auxiliary phase alloy (or referred to as liquid phase alloy, i.e. rare earth rich alloy, or referred to as grain boundary phase) are smelted, wherein the auxiliary phase alloy plays a main role in regulating main phase composition segregation, repairing grain boundary or implementing liquid phase sintering (ZHOU Shouzeng et al., Nd—Fe—B-sintering rare earth permanent magnet material and technology, Metallurgical Industry Press, Edition of September 2011, Chapter 12). In addition, sintering at 1050° C. to 1080° C. is conducted by a conventional technology in both two traditional preparation processes above, in this way, excellent magnet performances are not achieved and the preparation cost of magnet is increased.